The IPTV is a brand-new technology which integrates multiple technologies such as the Internet technology, the multimedia technology and the communication technology by virtue of a broadband cable television network and provides many kinds of interactive service such as the digital television service for home users. The user can enjoy IPTV service in two manners at home: (1) a computer, and (2) an IP set-top box plus an ordinary television set. The IPTV can be well adapted to the current rapid development trend of the network, and can fully and effectively utilize the network resource. The IPTV transmits manageable multimedia services such as television signals, videos, texts, graphs and data through an IP network on the premise of ensuring the quality of service/service experience, safety, interactivity and reliability. Thus, it can be seen that the IPTV is a manageable multimedia service in need of quality of service and safety guarantee, and is obviously different from an uncontrollable and unmanageable streaming media application on the Internet of which the quality and safety cannot be ensured.
The Real Time Streaming Protocol (RTSP) defines how to make a one-to-multiple application program effectively transmit multimedia data through the IP network, and the RTSP serves as the remote network control for a multimedia server.
At present, when using the IPTV, the user can only separately make a request of downloading or playing a media file to a CDN server through a set-top box, but cannot simultaneously download and play the media file. However, along with the continuous upgrade of the bandwidth available for users, such a separate downloading or playing mode may cause that a great lot of bandwidth is idled, and cannot meet the user's requirement on an IPTV service.